FAQ Answers

1. Why is the mission called Juno?

Juno, the god-sister-wife of Jupiter, maintained a constant, jealous
vigil over her god-husband's dalliances from Mount Olympus. When Jupiter
had his tryst with Io, he spread a veil of clouds around the entire
planet to conceal his activities. Upon observing the cloud-cloaked planet,
Juno immediately suspected Jupiter of concealing activities that would
not bear the light.

Hence, Juno came down from Mount Olympus and employed her special powers
to penetrate the clouds and reveal the true nature of Jupiter.

Listen to
Dr. Bolton (Juno Mission Principal Investigator) explain the choice
of the name of the mission.

2. How important for an understanding of the solar system do you believe
the Juno mission to be ?

To understand how the solar system formed we need to
understand how much oxygen (most commonly found as water) there is inside
Jupiter. Did Jupiter collapse from the original cloud of gas? Or, did
Jupiter form by the gravitational attraction of hydrogen gas onto a
core of ice and rock? Or, was more ice added later when large, left-over
ice balls collided with Jupiter? These different ideas all predict different
amounts of water in the outer layers of Jupiter. Unfortunately, scientists
have been unable to measure the amount of water at Jupiter.

3. How do scientists plan to use the information gathered about Jupiter
to understand water on Earth ?

Current ideas about the formation of the solar system
suggest that the Earth formed at about its present distance from the
Sun where it was too warm for ice to condense. This means that we think
that Earth formed from balls of rock and metal that condensed out of
the original cloud of gas close to the Sun. This means that the water
was delivered to the Earth later - after the planet was formed. One
possible source of water for the Earth is a population of large ice
balls that condensed out beyond the "frost line" (probably beyond the
asteroid belt) - ice balls left over from the formation of the cores
of Jupiter and the other giant planets. Being the largest, most-massive
planet in the solar system, Jupiter is thought to have stirred up the
left-over ice balls and sent them hurtling to the Earth. Some of these
ice balls may have been responsible for the large craters on the Moon.
The early phases of the solar system was a dangerous time!

4. Can you please describe the orbit paths of the Galilean satellites ?

The 4 Galilean satellites - Io, Europa, Ganymede and Callisto (in order away from Jupiter) - all have very circular orbits that lay very close to the equatorial plane of Jupiter. The inner 3 have very special orbits - these moons are in a orbital resonance. This means that for every once that Ganymede orbits Jupiter, Europa orbits almost exactly twice and Io almost exactly 4 times.

5. What one aspect of Jupiter interests you most and why ?

I am particularly interested in Jupiter's strong magnetic
field and the charged particles that are trapped by the planet's magnetic
field - similar to the Van Allen belts around the Earth (discovered
50 years ago by the first US rocket into space)!

6. Could you tell me about Jupiter's unique composition ?

Actually, the problem is that we really do not know Jupiter's
chemical composition. In particular, we would think that Jupiter should
have about the same composition of the Sun - after all, they both came
from the same large cloud of gas. But Jupiter seems to have higher amounts
of elements heavier than hydrogen and helium. In particular, we do not
know the amount of oxygen - the third most abundant element in the universe
after hydrogen and helium. That's why Juno is designed to measure the
amount of water at Jupiter... more about that later.